2,3,3,3-Tetrafluoropropene, which is a halopropene and represented by the chemical formula: CF3CF═CH2(HFO-1234yf), is a useful compound as a refrigerant. 2,3,3,3-Tetrafluoropropene has zero ozone depletion potential (ODP) and an extremely low global warming potential (GWP), and is thus drawing attention as a component of refrigerants, mixed refrigerants, and the like that can be used as an alternative for chlorofluorocarbon. Additionally, 2,3,3,3-tetrafluoropropene is useful not only as a propellant, heat transfer medium, or fire-extinguishing agent, but also as a monomer component in a polymer.
As a preparation process for preparing HFO-1234yf, for example, Patent Literature 1 discloses a preparation method in which a compound represented by CX3CHClCH2X (X is any halogen selected from F, Cl, Br, and I, and each X may be the same or different) is reacted with a Cr catalyst in the gas phase, thereby directly producing HFO-1234yf as a component of a product containing CF3CF═CH2 (HFO-1234yf). However, this method is not practical because its yield is low due to the formation of many impurities, and improvements are thus needed, and also because the catalyst is deteriorated in a short period of time.
Further, Patent Literature 2 listed below discloses a method for preparing HFO-1234yf in which HCC-1230xa represented by CH2ClCCl═CCl2 as a starting material is reacted with HF in the presence of a fluorinated catalyst so as to prepare HCFC-1233xf represented by CF3CCl═CH2, and further, HFO-1234yf is prepared via HCFC-244bb represented by CF3CFClCH3. However, this method has economic problems because the steps are complicated and long with many stages.
Additionally, Patent Literature 3 listed below discloses a method in which HCC-240 db represented by CCl3CHClCH2Cl as a starting material is reacted with HF in the gas phase at a reaction temperature of 255° C. in the presence of a fluorinated Cr catalyst. However, this method is not considered to be a practical preparation method of HFO-1234yf because HFO-1234yf is produced only in an amount of 0.5% in combination with HFC-245cb, and the main product is HCFC-1233xf (98.3% production).
Further, Patent Literature 4 listed below discloses a method for preparing HFO-1234yf in which HCC-1230xa represented by CH2ClCCl═CCl2 as a starting material is reacted with HF in the gas phase with oxygen entrainment in the presence of a fluorinated catalyst activated by HF at a pressure of 150 psi or higher, thereby preparing HFO-1234yf by a single-step reaction. However, because HCC-1230xa is used as a starting material in this method, catalyst deterioration due to olefin polymerization advances, and both oxygen entrainment and a stabilizer, such as a polymerization inhibitor, are required in order to inhibit the deterioration. This causes an increase in the economic cost.
As described above, all of these methods have problems, and therefore require further improvements. They are not considered to be effective methods for industrially preparing HFO-1234yf.